It is often desirable to perform positioning functions on user equipment (UE) such as a mobile terminal, laptop, wearable, tablet, a cellular phone or other mobile device. The terms “location” and “position” are synonymous and are used interchangeably herein. For example, in wireless systems based on the IEEE 802.11 standard, positioning may be performed using Round Trip Time (RTT) measurements between an Access Point (AP) and User Equipment (UE).
In modern wireless systems, multiple antennas at the transmitter and receiver may be used to implement multiple input/multiple output (MIMO). MIMO facilitates parallel delivery of multiple spatially multiplexed data signals, which are referred to as multiple spatial streams. In addition, “beamforming” may be used for directional signal transmission or reception. In beamforming, elements in a phased array antenna are combined so that signals at some angles experience constructive interference, while others experience destructive interference, so that the beam may be “steered” in a desired direction. Beamforming can be used to achieve spatial selectivity at the transmitting and receiving ends. Techniques to facilitate beamforming calibration may therefore provide improved UE location determination and/or channel characterization.